A general and rapid method to evaluate the effect of flow maldistribution on the performance of heat exchangers

Abstract

The effect of non-uniform flow on thermal performance of heat exchanger was analyzed in this paper. The quantitative relationships between velocity deviation factor and heat transfer coefficient, heat transfer capacity, entransy-dissipation-based thermal resistance, were obtained, respectively. Based on these relationships, an evaluation plot was proposed to evaluate the effect of flow maldistribution on thermal performance. The plot was divided into three zones according to various degrees of deterioration. In Zone Ⅰ (stable zone), the variations of amplitude of heat transfer characteristics is negligible with the increase of the velocity deviation factor. In Zone Ⅱ (deterioration zone), the increasing velocity deviation factor results in thermal performance reducing in a modest rate. In Zone Ⅲ (rapid deterioration zone), thermal performance deteriorates rapidly with the increase of velocity deviation factor. The predicted results of the evaluation plot were compared with abundant simulations and experiments from references, which cover cases of variable velocity deviation factors, different flow distribution profiles and various types of heat exchangers. The excellent agreement of the comparisons has proved that the plot can be successfully applied to rapidly evaluate the effect of non-uniform flow on thermal performance of heat exchanger with high accuracy. Meanwhile, traditional researches on thermal performance of heat exchanger with uniform flow can be easily translated into that of non-uniform flow by this plot method.